Add antipatterns repo

antipatterns/database-antipatterns.md

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+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+# Table of Contents
+
+- [Database anti-patterns](#database-anti-patterns)
+  - [Using `VARCHAR` instead of `TEXT` (PostgreSQL)](#using-varchar-instead-of-text-postgresql)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+
+Database anti-patterns
+======================
+
+Using `VARCHAR` instead of `TEXT` (PostgreSQL)
+----------------------------------------------
+
+Unless you absolutely restrict the width of a text column for data consistency
+reason, don't do it.
+
+This
+[benchmark](http://www.depesz.com/2010/03/02/charx-vs-varcharx-vs-varchar-vs-text/)
+shows that there's fundamentally no difference in performance between
+`char(n)`, `varchar(n)`, `varchar` and `text`. Here's why you should pick
+`text`:
+
+* `char(n)`: takes more space than necessary when dealing with values shorter
+  than n.
+* `varchar(n)`: it's difficult to change the width.
+* `varchar` is just like `text`.
+* `text` does not have the width problem that `char(n)` and `varchar(n)` and
+  has a cleaner name than `varchar`.